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Some pump and block experimentation fun

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Voodoo Rufus

Powder Junkie Moderator
Sep 20, 2001
Bakersfield, CA
I got some of my other pumps and unused hardware out for some semi-scientific testing fun. I have 4 DDC pumps that I've collected over time. Two 10W DDC310 Alphacool pumps, an 18W pump I got from Koolance or something, and a 6W pump that came as part of an EK DDC-Xres setup. The 6W pump has a 4-pin PWM power cable and an open impeller. Otherwise it's the same format as the other pumps. Maybe it's an SPC or something, not sure. Since I upgraded my main rig to the Optimus Signature V2 pump, my shiny V1 is sitting unused and without purpose. It has higher restriction than the V2 and a tad less performance, but not enough to see in the real world most likely. HardOCP did a great V1 review but their site is now offline I don't know how to find it now via a web archive or something.

From a TechPowerUp thread:

They did flow tests with several different blocks using a single D5, and a set of disconnects:

The EK supremacy evo had around 330l/h or 87.18gph
The Aquacomputer cuplex kryos next had around 296l/h or 78.20gph
The Optimus V1 had around 269l/h or 71.06gph

So the V1 flows 1.18gpm with a D5 hooked up. Good baseline for testing my DDC's. I also have a new HWLabs 360GTS radiator I never put to use. And plenty of 7/16" ID Tygon tubing.

How am I measuring flowrates? Well, all I have is a 500mL Pyrex measuring cup for lower flow rates, and a half gallon glass milk jar for the higher flow rate. Time taken in seconds to fill a fixed volume, then convert to gallons per minute.

The 18W flows a pretty hilarious amount of water at full speed through the radiator by itself. Some semi-scientific results of the 18W pump below.
Block + rad at 12V: ~.5gpm
Block + rad at 6.5V (about minimum pump speed): ~.2gpm.
Rad at 6.5V: ~.5gpm
Rad at 12V: ~2gpm. Whoa.

6W pump through block and rad at 12V: ~.2gpm. Terrible.

Now the bad news. The block upon disassembly had some organic buildup on the inside, necessitating a vinegar soak and soft toothbrush bristles to carefully remove. This was bound to affect the above results, so I will be updating the results again to see how bad the restriction was.

I did test the setup this morning by using the open impeller from the 18W pump sitting in the 6W motor assembly, pushing water through the cleaned block at 12V. This yielded .5GPM, which is respectable enough. It also somehow ended up pulling 8W instead of the 6W the motor is spec'ed for. Hopefully this won't hurt it.

Somewhere along the line since removing the V1 from my main rig I damaged the finish and gouged the copper. Now, Optimus does not recommend lapping their blocks because the brass top is designed to bend the base plate to the proper convex shape for best contact with IHS's or bare die operation when torqued down. But when the block is disassembled, or at least the screws loosened to unbend the base plate, the plate can then be lapped. I haven't done that in forever, but to remove the gouge I did the full work going from 400 grit to 600, 1500, then two grits of micron paper, followed by a 4000grit liquid polish to shine it up. From the methods I have available to gauge flatness, it will work just fine.

I will update all flow results soon.

My long term plans for this hardware is to actually use it in some sort of build, because the V1 was a limited run item, and radiators are cheap enough to not be worth trying to sell and ship. And since D5's are pretty much the pump of choice, not much point in trying to sell DDC's on the used market either. What I have in mind is a Lian Li O11D Mini build with the 360GTS mounted on the bottom pulling air in, the Xres with a DDC bolted to a universal 120mm fan frame mount, and the V1 bolted to either an 11th Intel CPU or AMD APU, as the Asrock X570 Phantom Gaming ITX has 115x mounts. Then it will be an HTPC rig geared towards minimum noise.


New results:
6W pump, 18W rotor, 12V, 8.5W: .5 GPM
6W pump, 6W rotor, 12V, 5.4W: .4 GPM - subjectively quieter than standard rotor, but would be insignificant inside a case
18W pump, 12V, 18W: 1.32 GPM
18W pump, 9.4V, 10W: .52 GPM - effectively simulates 10W DDC pump results
18W pump, 6.5V, 4.5W: .3 GPM - minimum pump speed before stall

Interesting! The 6W pump with the standard rotor effectively flows like the 10W pump at about a half gallon per minute. With the 4pin PWM it can easily be plugged into any motherboard fan header and be run flat out. Set it and forget it. The rotor it comes with does not flow very well and pretty much keeps the pump in AIO equivalent flow realm. The 18W pump at full power does handily cross the 1GPM threshold for real-world performance that would be well into the diminishing returns area for temps versus flow rate. Also, a plugged up Optimus block flows like crap! Be sure to run enough chemical in your real world systems to disallow organic growth.

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6W vs. 10/18W rotor:
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This place needs more posts like this! Thank you man. I'll have a cheap-o AM4 block coming in this week, and my "project" WB should be done this month as-well... looking forward to comparing them.
You're welcome! I felt the need to document my little fun, so may as well make it public like the articles I used to do.
And since D5's are pretty much the pump of choice, not much point in trying to sell DDC's on the used market either

Can't understand the DDC hate by everybody. Never had a problem with them and prefer the smaller footprint.
Only D5's I've owned both self destructed in a year or two. 6 DDC's still running. A couple are like ten years old.
Totally agree. I love my 10W DDC's. On a sound absorbent sponge they emit no noise outside of a decent case and run cool. I've never had one fail outside of my own stupidity either.
Another thing people tend to not realize is that an 18W DDC actually performs better than a D5 under real world conditions at the 1.5 GPM and less flowrates, at the expense of noise. But if you consider that a D5 is quieter at full speed compared to a DDC running at 3600rpm (a little more than 10W RPM at 3100 or so), it's easy to see why people go for them. My dual 10W DDCs are giving me roughly the same hydraulic performance as a single D5. I kind of have an itch to pick up a pair of Alphacool VPP755's and test them out.